A motor grader shapes or levels the ground by forcing a tool, such as a blade, to bear against the ground over which it is driven. For some applications, the grader is configured with a series of bits instead of a blade to better cut and break up the ground. For this configuration, the blade is replaced with an adapter board securing a plurality of bits.
Some bits are optimized for use in a forward-facing orientation. For example, they may have multiple tooling surfaces optimized to cut and shape the ground when the bit is maintained in a forward-facing orientation. The tooling surfaces may be made from a hard material, such as carbide, greatly reducing the tooling surface's wear rate and thereby increasing the bit's effective life. If such a bit is allowed to freely rotate, however, the other, non-tooling surfaces of the bit contact the ground, wearing the bit out far faster than when it is maintained in a forward-facing orientation.
Adapter boards of motor graders are generally designed to constrain the bits against rotation. For example, the underside of the adapter board may have a series of machined slots interlocking with the bits. Alternatively, a plurality of holes or slots in the adapter board may have non-circular cross-sectional shapes. For example, the slots may have rectangular or square cross sections. The bits may have corresponding non-circular shanks, such that once the shanks are received within a respective hole or slot in the adapter board, they are secured in a forward-facing orientation. Snap rings may be configured to attach to the bits to prevent them from falling out of the hole or slot in the adapter board.
The machined slots on the underside of the adapter board described above may help prevent rotation of the bits, but they may become worn as the underside of the adapter board scrapes and grinds against the ground. Once the machined slots have been completely worn away, they may fail to prevent rotation of the bits. Additionally, snap ring require specialized tools to remove, increasing the difficulty associated with removing and replacing the bits.
One exemplary system for securing bits in a forward-facing orientation is described in U.S. Pat. No. 4,913,125 (“the '125 patent”) which issued to Buntin et al. on Apr. 3, 1990. The shank of the bit, which is received within the holding device, has a rectangular cross section. The holding device has a complementary shaped slot for receiving the shank. To prevent the bit from falling out, a spigot and socket is provided.
Although the system of the '125 patent may help secure bits against rotation, machining non-circular slots is generally more costly and time consuming than drilling circular holes. Additionally, the spigot-and-socket configuration involves small, intricate parts, increasing both manufacturing cost and installation difficulty.
The disclosed system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.